Holy crap
Hey, waiter... that ain't no crab...1
But apparently (as Wikipedia tells me), "...in Northern Taiwan and other areas, they are not uncommon at seaside restaurants, served boiled and bisected with a clean lateral slice. The white meat, similar to crab or lobster in texture, is then easily removed."
(On one level, I realize that the distinction between crabs, shrimp, and lobster as "food" and other arthropods as "not food" is entirely arbitrary and cultural... on the other hand, those cultural distinctions can be pretty deeply ingrained....)
1 For those who are too lazy to click through to Wikipedia ;) this is a "Giant Isopod" -- think deep-sea potato bug. (Potato bugs / pill bugs, etc, are varieties of woodlice, and woodlice are a group of terrestrial crustaceans within the order Isopoda, the same order as this guy.)